The present invention pertains to a dispensing unit and system for liquid products, and more particularly to a system and unit wherein a plurality of different liquid products, such as condiments may be dispensed with controlled proportioning thereof.
One of the fastest growing industries, both here in the United States and in foreign countries, is that of the fast food franchise. Rising costs have necessitated employment of labor and time-saving devices to perform the various operations required in the preparation of the final, consumable product. One such operation which has proved to be both time-consuming and unreliable, is the controlled dispensing of condiments such as catsup, mustard, or the like, as used on hamburgers and other types of sandwiches. In this regard, the restauranteur is concerned not only with the labor involved, but also with the obtaining of uniformity in the amount of condiment dispensed, so as to maintain flavor standards and minimize waste.
In a related application, Ser. No. 664,556, now U.S. Pat. No. 4,032,044 there is disclosed a basic concept or system, including dispensing units, for the metered dispensing of liquid products, wherein a metering chamber is provided, and partially defined by a flexible wall or diaphragm. Through a control system different from that of the present invention, the force or pressure differential across this diaphragm is used to force said diaphragm into engagement with the opposite chamber wall, thus expelling a predetermined volume of condiment from the metering chamber.
The basic concept as disclosed and claimed in said application has wide application, and covers the present invention, which is in effect an improvement thereover. The particular dispensing units as shown in said application, utilize mechanical valving actions for controlling the flow of the liquid product to and from the metering chambers, which have proved troublesome in certain applications. More specifically, the term "mechanical valving" is used in a sense to connote valve arrangements of the type wherein one element, such as a valve spool, or a disc, is moved relative to an outer, ported element alternately to block and establish flow through said outer element. This type of a valve arrangement requires clearance between the relatively movable part as well as the use of seals to prevent leakage. While the mechanical type of valving action are totally adequate for liquid products which do not include a large percentage of suspended solids, when slurries or suspensions having high solid content are encountered such as mustard, these solids can penetrate the areas between the relatively movable parts tending to produce wear and clog or otherwise hinder the valving action.
As a further matter, when the liquid product to be dispensed is a food condiment, rigid sanitary and cleaning procedure must be adhered to. In this regard, it can be appreciated, that standard mechanical type valving actions do not lend themselves to ease of disassembly, cleaning and reassembly. The present invention, as will become clear from the discussion to follow, provides a convenient alternative to this problem.
With the dispensing unit of the present invention the expelling of the pressurized product from the metering chamber is achieved pursuant to the attainment of a pressure or force differential across the metering chamber diaphragm, which differential is produced by the alternate pressurization or venting of the side of the diaphragm opposite said chamber with respect to a pressurized medium such as nitrogen gas. As a further matter, the present invention also employs valve means for the control of the flow of the liquid product, which valve means are not subject to the numerous disadvantages of the mechanical type of valving as discussed above. More specifically, the valving action as contemplated by the present invention will be provided by a valve chamber defined partially by a cavity or concave wall surface having a weir extending thereacross, with a flexible diaphragm overlying said cavity and weir to define in effect a valve chamber. Valve inlet and outlet port communicate with the chamber on opposite sides of the weir, and means are provided for pressurizing the side of the diaphragm opposite the weir, to force the diaphragm into engagement with the weir and thereby block communication between the inlet and outlet ports.
As will become clear from the discussion to follow a separate diaphragm valve can be used to control the supply and discharge of the product from the metering chamber. The present invention, however, employs an ingenious arrangement whereby a single chamber functions both as the metering chamber and the valve means for controlling the supply of liquid product.
As an additional matter, it can be appreciated that in the unit as discussed above pressurization of the metering chamber and valve chamber diaphragms can be attained by using a pressure medium at a pressure level higher than that of the liquid product being supplied to the dispensing unit. The system of the present invention, however, provides a system whereby the operation of said diaphragms can be attained even through the pressurized medium and the liquid product are at substantially the same pressure. This arrangement, of course, greatly simplifies the overall system.
More specifically, with the present invention, even though the pressurized medium and the liquid product are at substantially the same pressure, the diaphragm type of valves will close quickly. This occurs, due to the fact that the pressure applied to the side of the diaphragm opposite the chamber is in effect a static or constant pressure which acts upon the full surface area of the diaphragm. On the other hand, the movement or flow of the liquid product through the respective chamber results in a pressure drop which is sufficient to create the differential that will commence movement of the diaphragm toward the chamber weir. As the diaphragm moves, increased throttling of the liquid product occurs which, in turn, results in an even greater pressure differential. Once the diaphragm is brought into engagement with the weir, the area on one side of the weir will be exposed to liquid product under pressure, while the area on the opposite side of the weir is subject only to ambient pressure. Thus, the force on the side of the diaphragm exposed to the pressurized medium will be greater than that created by the portion of the diaphragm exposed to the pressurized product and engagement of the diaphragm with the weir will be maintained.